A new method for generation of quasi-periodic structures withn fold axes: Application to five and seven folds

A new geometrical method for generating aperiodic lattices forn-fold non-crystallographic axes is described. The method is based on the self-similarity principle. It makes use of the principles of gnomons to divide the basic triangle of a regular polygon of 2n sides to appropriate isosceles triangles and to generate a minimum set of rhombi required to fill that polygon. The method is applicable to anyn-fold noncrystallographic axis. It is first shown how these regular polygons can be obtained and how these can be used to generate aperiodic structures. In particular, the application of this method to the cases of five-fold and seven-fold axes is discussed. The present method indicates that the recursion rule used by others earlier is a restricted one and that several aperiodic lattices with five fold symmetry could be generated. It is also shown how a limited array of approximately square cells with large dimensions could be detected in a quasi lattice and these are compared with the unit cell dimensions of MnAl6 suggested by Pauling. In addition, the recursion rule for sub-dividing the three basic rhombi of seven-fold structure was obtained and the aperiodic lattice thus generated is also shown.

Homonuclear NOE in spatially periodic spin systems

The nuclear Overhauser effect equations are solved analytically for a homonuclear group of spins whose sites are periodically arranged, including the special cases where the spins lie at the vertices of a regular polygon and on a one-dimensional lattice. t is shown that, for long correlation times, the equations governing magnetization transfer resemble a diffusion equation. Furthermore the deviation from exact diffusion is quantitatively related to the molecular tumbling correlation time. Equations are derived for the range of magnetization travel subsequent to the perturbation of a single spin in a lattice for both the case of strictly dipolar relaxation and the more general situation where additional T1 mechanisms may be active. The theory given places no restrictions on the delay (or mixing) times, and it includes all the spins in the system. Simulations are presented to confirm the theory.

土石混合体细观结构力学及其边坡稳定性研究

Soil-rock mixture (S-RM) refers to one extremely uneven loose rock and soil materials system with certain stone content. Its formation has started since Quaternary and it is composed of block stone, fine grained soil and pore with certain project scale and high strength. S-RM has extensive distribution in nature, especially in southwest China where the geotectonic background is complicated, the fracture activity is developed and the geomorphological characteristics of high mountain and steep gorge area are protuberant. This kind of complicated geologic body has developed wider in these areas. S-RM has obvious difference with the general soil or rock (rock mass) in physical and mechanical properties because its two components-“soil” and “rock-block” has extreme differences in physical and mechanical properties. The proposition of S-RM and its deep research are needed in the modern engineering construction. It is also the necessity in the modern development of rock and soil mechanics. The dissertation starts from the meso-structural characteristics of soil-rock and takes a systematic research on its meso-structural mechanics, deformation and failure mechanism and the stability of S-RM slope. In summary, it achieves the following innovative results and conclusions. There are various views on the conception of S-RM and its classification system. Based on the large number of field tests, the dissertation makes the conception and classification of S-RM more systematic. It systematically proposed the conception of meso-structural mechanics of S-RM. Thus the dissertation has laid a foundation for its deep study. With the fast development of the computer technology and digital image processing theory, digital image processing technology has been successfully applied in many fields and provided reliable technology support for the quantitative description of the structural characteristics of S-RM. Based on the digital image processing technology, the dissertation systematically proposes and developed the quantitative analysis method and quantitative index for the meso-structure of S-RM. The results indicate that the meso-structure such as its internal soil-rock granularity composition, the soil-rock shape and the orientability has obvious self-organization in the macro statistical level. The dissertation makes a systematic research on the physical mechanical properties, deformation and failure mechanism of S-RM based on large field test. It proposes the field test for the underwater S-RM and deduces the 3D data analysis method of in-situ horizontal push-shear test. The result indicates that S-RM has significant phenomenon of shear dilatancy in the shearing process, and its dilatancy will be more obvious with the increased proportion of rock or the decreased confining pressure. The proportion of rock has great effect on the strength of S-RM and rock-block, especially the spatial position of particles with comparatively big size has great effect on the shape and spatial position of the sample shear zone. The dissertation makes some improvements in the single ring infiltration test equipment and its application on the permeability of S-RM. The results indicate that the increasing of rock-block would make it more difficult for the soil to fill in the vacuity between the rock-block and the proportion would increase which would result in the increased permeability coefficient. The dissertation builds the real meso-structural model of S-RM based on the digital image processing technology. By using geometric reconstruction technology, it transfers the structural mode represented by Binary image into CAD format, which makes it possible to introduce the present finite element analysis software to take research on numerical experimental investigation. It systematically realizes leaping research from the image，geometric mode, to meso-structural mechanics numerical experiment. By using this method, the dissertation takes large scale numerical direct-shear test on the section of S-RM. From the mesoscopic perspective, it reveals three extended modes about the shear failure plane of S-RM. Based on the real meso-structural model and by using the numerical simulation test, the character and mechanics of seepage failure of S-RM are studied. At the same time, it builds the real structural mode of the slope based on the analysis about the slope crosssection of S-RM. By using the strength reduction method, it takes the research on the stability of S-RM and gets great achievements. The three dimensional geometric reconstruction technology of rock block is proposed, which provides technical support for the reconstruction of the 3D meso-structural model of S-RM. For the first time, the dissertation builds the stochastic structure model of two-dimensional and three-dimensional polygons or polyhedron based on the stochastic simulation technique of monte carlo method. It breaks the traditional research which restricted to the random generation method of regular polygon and develops the relevant software system (R-SRM2D/3D) which has great effect on meso-structural mechanics of S-RM. Based on the R-SRM software system which randomly generates the meso-structural mode of S-RM according to the different meso-structural characteristics, the dissertation takes a series of research on numerical test of dual axis and real three-axis, systematically analyses the meso destroy system, the effects of meso-structural characteristics such as on the stone content, size composition and block directionality on the macro mechanical behavior and macro-permeability. Then it proposes the expression of the upper and lower limit for the macro-permeability coefficient of the inhomogeneous geomaterials, such as S-RM. By using the strength reduction FEM, the dissertation takes the research on the stability of the slope structural mode of the randomly formed S-RM. The results indicate that generally, the stability coefficient of S-RM slope increases with the increasing of stone content; on the condition of the same stone content, the stability coefficient of slope will be different with different size composition and the space position of large block at the internal slop has great effect on the stability. It suggests that meso-structural characteristics, especially the space position of large block should be considered when analyzing the stability of this kind of slope and strengthening design. Taking Xiazanri S-RM slope as an example, the dissertation proposes the fine modeling of complicated geologic body based on reverse engineering and the generation method of FLAC3D mode. It resolves the bottleneck problem about building the fine structural mode of three-dimensional geological body. By using FLAC3D, the dissertation takes research on the seepage field and the displacement field of Xiazanri S-RM slope in the process of reservoir water level rising and decreasing. By using strength reduction method, it analyses the three-dimension stability in the process of reservoir water level rising and decreasing. The results indicate that the slope stability firstly show downward trend in the process of reservoir water level rising and then rebound to increase; the sudden drawdown of reservoir water level has great effect on the slope stability and this effect will increase with the sudden drawdown amplitude rising. Based on the result of the rock block size analysis of S-RM, and using R-SRM2D the stochastic structure model of Xiazanri S-RM slope is built. By using strength reduction method, the stability of the stochastic structure model is analysis, the results shows that the stability factor increases significantly after considering the block.

Solidarity in Choosing a Location on a Cycle

We study the implications of two solidarity conditions on the efficient location of a public good on a cycle, when agents have single-peaked, symmetric preferences. Both conditions require that when circumstances change, the agents not responsible for the change should all be affected in the same direction: either they all gain or they all loose. The first condition, population-monotonicity, applies to arrival or departure of one agent. The second, replacement-domination, applies to changes in the preferences of one agent. Unfortunately, no Pareto-efficient solution satisfies any of these properties. However, if agents’ preferred points are restricted to the vertices of a small regular polygon inscribed in the circle, solutions exist. We characterize them as a class of efficient priority rules.

Nonlinear Control Strategies for Cooperative Control of Multi-Robot Systems

This thesis deals with distributed control strategies for cooperative control of multi-robot systems. Specifically, distributed coordination strategies are presented for groups of mobile robots. The formation control problem is initially solved exploiting artificial potential fields. The purpose of the presented formation control algorithm is to drive a group of mobile robots to create a completely arbitrarily shaped formation. Robots are initially controlled to create a regular polygon formation. A bijective coordinate transformation is then exploited to extend the scope of this strategy, to obtain arbitrarily shaped formations. For this purpose, artificial potential fields are specifically designed, and robots are driven to follow their negative gradient. Artificial potential fields are then subsequently exploited to solve the coordinated path tracking problem, thus making the robots autonomously spread along predefined paths, and move along them in a coordinated way. Formation control problem is then solved exploiting a consensus based approach. Specifically, weighted graphs are used both to define the desired formation, and to implement collision avoidance. As expected for consensus based algorithms, this control strategy is experimentally shown to be robust to the presence of communication delays. The global connectivity maintenance issue is then considered. Specifically, an estimation procedure is introduced to allow each agent to compute its own estimate of the algebraic connectivity of the communication graph, in a distributed manner. This estimate is then exploited to develop a gradient based control strategy that ensures that the communication graph remains connected, as the system evolves. The proposed control strategy is developed initially for single-integrator kinematic agents, and is then extended to Lagrangian dynamical systems.

Tessellation with some Irregular Poligons

An idea for the use of problems of tessellation with irregular polygons in the optional activities in Information Technologies teaching are presented.

Identifying key belief-based targets for promoting regular physical activity among mothers and fathers with young children

We investigated the key beliefs to target in interventions aimed at increasing physical activity (PA) among mothers and fathers of young children. Parents (288 mothers and 292 fathers) completed a Theory of Planned Behaviour belief-based questionnaire and a 1-week follow-up of PA behaviour. We found that a range of behavioural, normative, and control beliefs were significantly correlated with parents’ PA intentions and behaviour, with only a few differences observed in correlations between PA beliefs and intention and behaviour by gender. A range of key beliefs was identified as making independent contributions to parents’ PA intentions; however, the behavioural beliefs about improving parenting practices (β = 0.13), interfering with other commitments (β = −0.29); normative beliefs about people I exercise with (β = 0.20); and control beliefs about lack of time (β = −0.24), inconvenience (β = −0.14), lack of motivation (β = −0.34), were revealed as significant independent predictors of actual PA behaviour. Furthermore, we found that a limited amount of parents already hold these beliefs, suggesting that these key beliefs warrant changing and, therefore, are appropriate targets for subsequent intervention. The current study fills an empirical gap in the PA literature by investigating an at-risk group and using a well established theoretical framework to identify key beliefs that guide parents’ PA decision-making. Overall, we found support for parents being a unique group who hold distinctive behavioural, normative, and control beliefs toward PA. Attention to these key underlying beliefs will assist intervention work aimed at combating inactivity among this at-risk population.

Regular exercise participation mediates the affective response to acute bouts of vigorous exercise

Physical inactivity is a leading factor associated with cardiovascular disease and a major contributor to the global burden of disease in developed countries. Subjective mood states associated with acute exercise are likely to influence future exercise adherence and warrant further investigation. The present study examined the effects of a single bout of vigorous exercise on mood and anxiety between individuals with substantially different exercise participation histories. Mood and anxiety were assessed one day before an exercise test (baseline), 5 minutes before (pre-test) and again 10 and 25 minutes post-exercise. Participants were 31 university students (16 males, 15 females; Age M = 20), with 16 participants reporting a history of regular exercise with the remaining 15 reporting to not exercise regularly. Each participant completed an incremental exercise test on a Monark cycle ergometer to volitional exhaustion. Regular exercisers reported significant post-exercise improvements in mood and reductions in state anxiety. By contrast, non-regular exercisers reported an initial decline in post-exercise mood and increased anxiety, followed by an improvement in mood and reduction in anxiety back to pre-exercise levels. Our findings suggest that previous exercise participation mediates affective responses to acute bouts of vigorous exercise. We suggest that to maximise positive mood changes following exercise, practitioners should carefully consider the individual’s exercise participation history before prescribing new regimes.

A free weekly iron-folic acid supplementation and regular deworming program is associated with improved hemoglobin and iron status indicators in Vietnamese women

Background Anemia due to iron deficiency is recognized as one of the major nutritional deficiencies in women and children in developing countries. Daily iron supplementation for pregnant women is recommended in many countries although there are few reports of these programs working efficiently or effectively. Weekly iron-folic acid supplementation (WIFS) and regular deworming treatment is recommended for non-pregnant women living in areas with high rates of anemia. Following a baseline survey to assess the prevalence of anemia, iron deficiency and soil transmitted helminth infections, we implemented a program to make WIFS and regular deworming treatment freely and universally available for all women of reproductive age in two districts of a province in northern Vietnam over a 12 month period. The impact of the program at the population level was assessed in terms of: i) change in mean hemoglobin and iron status indicators, and ii) change in the prevalence of anemia, iron deficiency and hookworm infections. Method Distribution of WIFS and deworming were integrated with routine health services and made available to 52,000 women. Demographic data and blood and stool samples were collected in baseline, and three and 12-month post-implementation surveys using a population-based, stratified multi-stage cluster sampling design. Results The mean Hb increased by 9.6 g/L (95% CI, 5.7, 13.5, p < 0.001) during the study period. Anemia (Hb<120 g/L) was present in 131/349 (37.5%, 95% CI 31.3, 44.8) subjects at baseline, and in 70/363 (19.3%, 95% CI 14.0, 24.6) after twelve months. Iron deficiency reduced from 75/329 (22.8%, 95% CI 16.9, 28.6) to 33/353 (9.3%, 95% CI 5.7, 13.0) by the 12-mnth survey, and hookworm infection from 279/366 (76.2%,, 95% CI 68.6, 83.8) to 66/287 (23.0%, 95% CI 17.5, 28.5) over the same period. Conclusion A free, universal WIFS program with regular deworming was associated with reduced prevalence and severity of anemia, iron deficiency and ho

Anchoring and exposing in the third place : regular identification at the boundaries of social realms

Harry’s is my favourite bar in my neighbourhood. It is a small wine bar, owned by three men in their late thirties and targeted at people like them; my gentrifying inner city neighbourhood’s 20 to 40 something urban middle class. Harry’s has seats along the bar, booths inside, and a courtyard out the back. The seating arrangements mean that larger groups tend to gather outside, groups of two to four spread around the location, and people by themselves, or in groups of two, tend to sit at the bar. I usually sit at the bar....

Actor 1 (Icecream Coles Polygon)

A sculpture made of polyurethane, epoxy resin, pigment and lacquer depicting a ice-cream melting into the form of a nine sided geometric figure.

Fibre diffraction of lithium DNA shows structural variability and deviation from a regular helical structure for the B-form

Recently, reports have appeared which show structural variations in B-DNA and indicate deviations from a uniform helical structure. We report for the first time that these indications are also present in the B-form fibre diffraction patterns for the lithium salt of natural DNA. We have used an improved method of controlling the salt concentration in the fibres. Our results are based on the appearance and disappearance of meridional reflections on different layer lines depending upon the salt.

Multipath Dissemination in Regular Mesh Topologies

Mesh topologies are important for large-scale peer-to-peer systems that use low-power transceivers. The Quality of Service (QoS) in such systems is known to decrease as the scale increases. We present a scalable approach for dissemination that exploits all the shortest paths between a pair of nodes and improves the QoS. Despite th presence of multiple shortest paths in a system, we show that these paths cannot be exploited by spreading the messages over the paths in a simple round-robin manner; nodes along one of these paths will always handle more messages than the nodes along the other paths. We characterize the set of shortest paths between a pair of nodes in regular mesh topologies and derive rules, using this characterization, to effectively spread the messages over all the available paths. These rules ensure that all the nodes that are at the same distance from the source handle roughly the same number of messages. By modeling the multihop propagation in the mesh topology as a multistage queuing network, we present simulation results from a variety of scenarios that include link failures and propagation irregularities to reflect real-world characteristics. Our method achieves improved QoS in all these scenarios.